1. Field of the Invention
The present invention relates to a multiple examination arrangement of the type having a number of imaging systems that are located in one space such that a patient lying on a movable patient support table can be examined in each of the imaging systems without changing beds.
2. Description of the Prior Art
Multiple examination arrangements such as the type described above have been proposed many times. Besides the combination described in U.S. Pat. No. 5,615,430 of a linear accelerator with a computed tomography system, other combinations of imaging systems have already been contemplated. A common drawback of all these proposals is that they have not been designed to give adequate consideration to the mutual influence of the systems, and in none of these proposals are any specific measures taken to avoid interference effects of the fields of one system on the other systems.
An object of the present invention is to provide a multiple examination arrangement that is suitable for medical diagnosis, particularly for interventional diagnosis, which offers the additional advantage of a more extensive use for simultaneously examining different patients, besides the simplified examining of one patient in several imaging systems.
This object is inventively achieved in a multiple examination arrangement that, besides an MR system having an actively shielded magnet, has a radiographic angiography system having a soft-magnetic covering for shielding from the static stray field of the MR system. The radiographic angiography system preferably is laterally offset relative to the z-axis of said magnet of the MR system.
The combination of an MR system with a radiographic angiography system represents the unification of two particularly essential imaging systems for medical diagnosis whose simultaneous utilization in one examination space has not been accomplished heretofore due to the strong fields that influence the other device.
The construction of the MR device with an actively shielded magnetxe2x80x94so that only a quadrupolar stray field that decays rather sharply with distance can penetrate beyond the shieldingxe2x80x94together with the displacement of the radiographic angiography system laterally relative to the z-axis of the magnet of the MR system, combined with the additional soft-magnetic shielding of the imaging parts of the radiographic angiography system, achieve a mutual decoupling of such a nature as to enable simultaneous operation of both systems in one space without significant mutually interfering influences.
In an embodiment of the invention the magnet of the MR system is provided with a field stabilizing system (E.I.S.) that has ferromagnetic coils at the face sides of the magnet. This compensates for interfering influences on the field homogeneity in the center of the magnet caused by ferromagnetic parts, particularly moving or shifted parts, in the environment i.e., it prevents undesirable feedback caused by the shielding parts of the radiography system.
The ferromagnetic shielding elements at the radiographic angiography system should be arranged substantially symmetrically around the axis, or corresponding balancing elements should be installed, so that, as a consequence of the symmetry in rotational movements, the magnetic resonance magnets optimally do not exert any influence on the homogeneity from the outset.
In addition to these shieldings as described above, it has proven particularly expedient to shield the electronics of the radiographic angio system at least partially against emerging electromagnetic interference radiation, and to construct the electronics such that its unshielded regions can be separately shut off and/or deactivated into a xe2x80x9csleep mode.xe2x80x9d In this way, no electromagnetic interference radiation can influence the measuring of the magnetic resonance signals.
At least in the regions of the support table in which the patient lying thereon is to be X-rayed, the patient support table should consist of a material that is MR-compatible, particularly a material having a low electrical conductivity and a small loss factor, and which is non-ferromagnetic. Furthermore, the material should exhibit only a low X-ray absorption, and should be substantially homogenous.
Based on this construction of the patient support table, it is also possible for the patient support table to be provided in a particularly simple manner with longitudinally displaceable removable plates and to be mounted on a column that can be rotated around the intersection of the insertion axes of the magnetic resonance system and the radiographic angiography system. It has proven particularly advantageous to construct the top support table plate of the patient support table as the insertion transport plate for the magnetic resonance system.
Based on this particular type of allocation of the MR system and the radiographic angio system relative to one another and of the patient support table that can be moved into position for insertion into both imaging systems by simple rotation around the column, a particularly simple and rapid examination sequence is possible, which is of importance in view of the high cost of such systems and the high degree of utilization thereof thus required.